α-alumina, slurry, porous membrane, laminated separator, and nonaqueous electrolyte secondary battery and method for producing same

Abstract

An object of the present invention is to provide an alumina used for a slurry for reducing unevenness in a surface of a porous membrane. The present invention is an α-alumina wherein a crystallite size obtained by a Rietveld analysis is not greater than 95 nm, and a lattice strain obtained by the Rietveld analysis is not greater than 0.0020. A BET specific surface area by a nitrogen adsorption method of the α-alumina is preferably not greater than 10 m 2 /g. A particle diameter D50 equivalent to 50% cumulative percentage by volume of the α-alumina is also preferably not greater than 2 μm.

The invention claimed is: 
     
       1. An α-alumina wherein
 a crystallite size obtained by a Rietveld analysis is not greater than 95 nm, and 
 a lattice strain obtained by the Rietveld analysis is not greater than 0.0020. 
 
     
     
       2. The α-alumina according to  claim 1 , wherein a BET specific surface area by a nitrogen adsorption method is not greater than 10 m 2 /g. 
     
     
       3. The α-alumina according to  claim 1 , wherein a particle diameter D50 equivalent to 50% cumulative percentage by volume is not greater than 2μm. 
     
     
       4. The α-alumina according to  claim 1 , wherein
 the crystallite size is not less than 50 nm and not greater than 95 nm, and 
 the lattice strain is not less than 0.0001 and not greater than 0.0010. 
 
     
     
       5. A slurry comprising:
 the α-alumina according to  claim 1 ; 
 a binder; and 
 a solvent. 
 
     
     
       6. A porous membrane comprising the α-alumina according to  claim 1 . 
     
     
       7. A laminated separator comprising:
 a separator; and 
 the porous membrane, according to  claim 6 , laminated on at least one of surfaces of the separator. 
 
     
     
       8. A nonaqueous electrolyte secondary battery comprising:
 a positive electrode; 
 a negative electrode; 
 a nonaqueous electrolyte; and 
 a separator, wherein 
 the porous membrane according to  claim 6  is formed on at least one of surfaces of the positive electrode, the negative electrode, and the separator. 
 
     
     
       9. A method for producing a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator, the method comprising:
 applying the slurry according to  claim 5  to at least one of surfaces of the positive electrode, the negative electrode, and the separator; and 
 drying the slurry to form a porous membrane on the at least one of the surfaces. 
 
     
     
       10. The α-alumina according to  claim 2 , wherein a particle diameter D50 equivalent to 50% cumulative percentage by volume is not greater than 2 μm. 
     
     
       11. The α-alumina according to  claim 10 , wherein
 the crystallite size is not less than 50 nm and not greater than 95 nm, and 
 the lattice strain is not less than 0.0001 and not greater than 0.0010.